1. Technical Field
The present invention relates to a fuel injection controlling system of an internal combustion engine.
2. Background Art
An internal combustion engine (hereunder referred to as “engine”) to feed intake air volume by operating an IAVC (Idle Air Control Valve) or the like in an idle speed region is known. Meanwhile, a technology of controlling the intake air volume in an idle speed region by a TBW (Throttle By Wire) method is also known. In the TBW method, the variable of an accelerator grip manipulated by a user, namely an accelerator opening degree, is detected and a throttle valve motor to open and close a throttle valve is driven based on the detected accelerator opening degree.
In the meantime, the distance between a combustion chamber and a throttle valve is shorter in the intake system of a motorcycle than in that of a four-wheeled vehicle. Moreover, the valve overlap of intake and exhaust valves increases in the case of a higher output engine or the like. When an engine is used for a long period of time in a motorcycle having such features, it may be sometimes required particularly to take it into consideration that: carbon blown back from the side of a combustion chamber to an intake air path adheres to a throttle valve; an intake air quantity characteristic to a throttle opening degree changes; and an air-fuel ratio deviates to a side richer than anticipated.
In view of such a situation, for example Japanese Patent No. 4056413 proposes an idle rotation speed controller of an engine that can grasp the situation of carbon accumulation and correct the opening degree of a throttle valve on the basis of a learned value of a throttle opening degree.
A conventional controller described in Japanese Patent No. 4056413 is a device that corrects carbon in order to maintain an idle rotation speed in a normal state and is not a device that corrects an injected fuel quantity in other operation regions. Particularly in a motorcycle wherein throttle operation is manually applied therefore, there has been room for further improvement in order to satisfy a user sensitive to an engine output characteristic in a low throttle opening degree region exceeding an idling region. In the case of computing a basic injection quantity by using an engine rotation speed (Ne)—intake air vacuum (Pb) map or an Ne—throttle opening degree (Th) map in particular, it has been particularly wanted that the injected fuel quantity is changed smoothly without a feeling of strangeness when the Nb—Pb map is switched to the Ne—Th map during low load operation.